The present invention relates to binoculars capable of two-stage magnification change; more specifically, it relates to two-stage variable power binoculars configured so that the size of the apparent field of vision does not change when the magnification is changed.
With conventional variable power binoculars a zoom knob and zoom lever are rotated to change magnification continuously. However, such binoculars tend to lack instantaneousness when magnification is changed.
Two-stage variable power binoculars are known as variable power binoculars that instantaneously change magnification. Two-stage variable power binoculars are configured such that magnification is changed by sliding operation of a focal adjustment knob, and focal adjustment is made by rotational operation of the same (see, for example, patent reference 1).
Patent reference 1: Laid-open Japanese Utility Model S63-65013
The two-stage variable power binoculars of patent reference 1 are configured such that a focal adjustment knob is provided that can slide or rotate in the optical axis direction, and at the time of a prescribed magnification (for example, magnification of 10), the focal adjustment knob is slid in a set direction to move a magnification switch lens off the optical axis, and in this state, the focal adjustment knob is rotated to adjust focus.
When magnification is to be changed (for example, to a magnification of 20), the focal adjustment knob is slid in the reverse direction to return the magnification switch lens to the optical axis, and in this state, the focal adjustment knob is rotated to adjust focus.
Such two-stage variable power binoculars are configured so that when the focal adjustment knob is operated to focus on an object, the magnification switch lens is prevented from moving from a position once it has been set.
Therefore, when magnification is to be returned to the original setting, the focal adjustment knob is again slid in the reverse direction to change magnification, and the focal adjustment is carried out using the same operation as described above.